The definitive analysis of Indo-European in its time, Hirt's grammar (1921–1937) is a monument of the German philological tradition.

Hermann Alfred Hirt (1865–1936) taught Greek, Latin and early Germanic languages at Leipzig University from 1892 to 1912 before moving to the chair of Sanskrit and comparative linguistics at Giessen. Born around the time when Bopp and Schleicher were publishing their ground-breaking work on Indo-European, and a young man when Brugmann published his monumental comparative grammar (all available in this series), Hirt began this seven-volume grammar in the 1920s soon after the exciting discovery of Tocharian and the decipherment of Hittite. The project arose out of his extensive research on the historical phonology of Indo-European vowels, which led him to consider much wider issues. Volume 3 (1927) is devoted mainly to the noun system in the Indo-European languages, focusing first on indeclinable nouns and moving on to nominal declensions. He also discusses adjectives, interjections, and gender, as well as stem formation.